1. Field of the Invention
The present invention concerns a trailer coupling to connect a semitrailer with a tractor. In trailer couplings of this type, the vertical forces are transmitted from the semitrailer to the tractor by means of a coupling plate mounted on the latter, the coupling plate slidingly cooperates with a slide plate fastened to the semitrailer.
2. Description of the Prior Art
In order to insure the uninhibited movement of the plates with respect to each other, especially when the unit is travelling over curves, friction between the plates must be reduced as much as possible. In place of the still widely used grease lubrication, a trailer coupling is described in U.S. Pat. No. 3,337,277, incorporated herein by reference, wherein an anti-friction layer of polytetrafluoroethylene (PTFE) or another suitable synthetic plastic, is applied to the surface of the coupling plate, which is in sliding cooperation with the slide plate mounted on the trailer, to the free surface of which a sliding layer may also be applied.
The disadvantage of the known configuration is the relatively great wear to which the anti-friction layer or layers are exposed in travel. A principal cause of this wear is the fact that in the known configuration, no pairing or mating can be established among the plates as they wear together during operation, because in the normal operation of a truck tractor, different trailers may be attached alternatingly and the constantly changing surface structures lead to rapid wear of the anti-friction layers.